Introduction

This page is there to answer the common question:
"My CPU is running at xx degrees, is it too hot?". Here are the
maximum
temperatures for the most popular CPUs.

Keep in mind that the onboard measurement facilities are often
inaccurate
and may report temperatures that are too low. This is especially the
case
with motherboards that use a thermal sensor below the CPU to "guess"
the
CPU temperature. The temperature values displayed by the BIOS have
usually
a correction value added, to compensate for this problem - but in some
cases
this correction value may be too low, or the sensor might not be in
good
contact with the CPU.

This means: If the maximum allowed temperature for your CPU is
95°C,
and your motherboard reports a CPU temperature of 90°C, then you
are not on the safe side.

However, this doesn't mean that you should start to panic when
your
Athlon XP CPU reaches 60 degrees celsius, for example. Most people tend
to
underestimate normal CPU operating temperatures - maybe due to
overclockers
bragging with their super-low CPU temperatures in forums.

Also, note that these values are for CPUs
that are not overclocked. Overclocked CPUs may run unstable
even
if their temperature is way below the maximal specified temperature.

What happens if the maximum operating temperatures are exceeded?

If your cooler is insufficient and the
temperature exceeds the maximum operating temperature, then this does
not
mean that the CPU is automatically damaged. With AMD CPUs, you will
usually
encounter crashes if the CPU is overheated; but these go away as soon
as
the CPU is cooler again. In the long term, running the CPU at a
temperature
that is too high may reduce the CPU life, since an overheated CPU is
more
prone to electromigration - even if it runs stable. With P4 CPUs, the
CPU
will turn its speed down automatically when it overheats. No damage to
the
CPU is possible, but the system will get slower while it's hot (which,
in
some cases, users might not even notice).

If you attempt to operate a CPU without
heatsink at all, recent AMD CPUs will usually be permanently damaged
within
seconds, unless special protection circuitry is available on the
motherboard.
P4 CPUs will run excessively slow without cooler.

The purpose of this page is to give you a quick overview of typical
maximum operating temperatures for common CPUs. In the case of Intel
CPUs, values vary a bit; if you need precise information for one
specific CPU model, please use the datasheets on the CPU manufacturer's
website, or visit Chris
Hare's
Processor Electrical Specifications page - there, you will find
more details, and also data for more exotic CPU types than the ones
covered here.

Higher is better here

On cooling-related websites, lower temperatures typically correspond to better products. On this
particular page, the opposite is true: The higher temperatures a CPU can withstand, the less cooling
is required. CPUs with low electrical power, but high temperature rating can be used with more quiet
and more compact coolers. An example for such a CPU is the Pentium-M, which dissipates less than 25
watts, but may reach temperatures of up to 100°C. The worst-case example is the Pentium 4 Extreme
Edition 3.46GHz, which dissipates over 110 watts, but may only reach a maximum temperature of
66°C. Obviously, you need a large and possibly loud cooler here.

The actual data:

AMD Athlon, Athlon 64, Opteron, Duron
and Sempron

All Slot A CPUs (Athlon classic,
Athlon Thunderbird)

70°C

Athlon Socket A up to 1 GHz, Duron up to 1.3GHz

90°C

Athlon "Thunderbird" Socket A 1.1GHz
or more

95°C

Athlon MP 1.33GHz or more

95°C

Athlon XP up to 2100+

90°C

Athlon XP 2200+ and faster

85°C

Duron "Applebred" 1.4G and faster

85°C

AMD Opteron

69 or 70°C
depending
on model

Athlon 64, 64FX, Sempron

Most models 70°C; 65°C for some Socket 939 Athlon 64 models

Athlon 64 X2 (dual core)

65°C

AMD K6 series

All K6 CPUs
(166-300MHz) and most K6-2/K6-III CPUs

70°C

K6-2/K6-III CPUs, model name ending with X (e.g. K6-2-450AFX)

65°C

K6-2-400AFQ (uncommon)

60°C (!)

K6-2+, K6-III+, most mobile K6/K6-2 CPUs

85°C

mobile K6/K6-2 model name ending with K
(e.g. mobile K6-2-P-400AFK)

80°C

The temperatures specified for AMD
CPUs max case surface temperatures. These CPUs do not have an internal
diode
to measure CPU temperature. The accuracy of the CPU temperature
measurement depends on the motherboard; therefore, it is possible that
the CPU overheats even though the CPU temperature reported by the
motherboard is below the specified
maximal temperature.

Note: Pentium 4 and Pentium D temperature specifications indicate
the maximum cover temperature, which is typically lower than the
temperature reported by the internal thermal diode. Therefore, your
system may be running fine even if the reported "CPU temperature" in
the BIOS is higher than the temperature specified here. This does
not mean that you're on the safe side, though.

Intel Pentium Pro

Pentium Pro,
256 or 512K L2 cache

85°C

Pentium Pro, 1MB L2 cache

80°C

Pentium Pro temperatures are maximum surface temperatures.

Typical maximum power usage of common CPUs and overclocked CPUs

Apart from the maximum CPU operating temperature, the maximum
power usage under typical worst-case conditions (thermal design power)
is also essential for selecting a suitable cooling system. To find
out about CPU power usage, please check out Chris
Hare's Processor Electrical Specifications page. There, you will
find values for unoverclocked CPUs running at their specified
voltage.

How can you estimate power usage of an overclocked CPU based on this value?

The theory behind calculating the power usage
for an overclocked CPU is very simple: Power usage is proportional to clock
speed, and proportional to the square of the core voltage.

Before we express this as a formula, let's intruduce the following variables:

Ps is the power usage of the non-overclocked
CPU

Po is the power usage of the overclocked CPU

Fs is the clock speed of the non-overclocked
CPU

Fo is the clock speed of the overclocked CPU

Us is the default voltage of the non-overclocked
CPU

Uo is the voltage at which the overclocked
CPU runs

Here is the formula:

Po = Ps * (Fo/Fs) * (Uo2/Us2)

A simple example:

We want to calculate the maximum power
usage of a Athlon "Thunderbird" 1.33 GHz CPU overclocked to 1.6GHz
using 1,9V voltage. From this page, we find out that:

Ps is 70W (max)

Us is 1.75V

Also, we know that

Fs is 1.33GHz

Fo is 1.6GHz

and Uo is 1.9V

Therefore:

Po = 70 W * (1.6/1.33) * (1.92/1.752)
= 99.26 W

Values calculated using this method are not very accurate, since I/O voltage and FSB speed is not taken into account.
However, they should be precise enough to help you decide what kind of power supply and cooling you need.

Disclaimer

The information here is provided WITHOUT
WARRANTY of any kind. If you are designing a system and need to have
accurate
information on the maximum temperature of a specific CPU, please rely
on
the information provided by the CPU manufacturer, and not the
information
here.

Last update: December, 2004. Future CPU models (even if they are
marketed under the same name/with the same MHz) as
the CPUs mentioned here may have different thermal specifications.